1. Field of the Invention
The present invention relates to a drive unit (e.g., an integrated drive unit, or a wheel drive unit), and, more specifically, to an improved drive unit including an improved disconnect device for selectively disengaging the input shaft from the gear reduction train to allow the gear reduction train to freewheel.
2. Description of the Related Art
Wheel drive units include a single housing having a transmission connectable to a power source mounted exterior of the housing. In one known wheel drive unit, a sleeve is utilized to link a power source to an input shaft selectively drivingly engaged with the transmission. In some configurations, the wheel drive unit is configured to accommodate axial displacement of the input shaft to allow the input shaft to be disengaged from the transmission so that the wheel drive unit will freewheel.
Integrated drive units include a single housing containing both a power input device and a transmission. The power input device can be, e.g., a hydraulic motor. In one known integrated drive unit, the hydraulic motor is linked to the transmission of the integrated drive unit via an output shaft (drivingly engaged with the motor) coupled to an input shaft (selectively drivingly engaged with the transmission). In some configurations, the integrated drive unit is configured to accommodate axial displacement of the input shaft to allow the input shaft to be disengaged from the transmission so that the integrated drive unit will freewheel. For the purposes of this document, xe2x80x9cdrive unitxe2x80x9d generically refers to either a wheel drive unit or an integrated drive unit.
One known drive unit utilizes an externally positioned cover or xe2x80x9chatxe2x80x9d to position the input shaft in either an engaged or a disengaged position. The hat includes a protrusion having a hollow interior sized to accommodate a plunger pin which abuts the input shaft. When the input shaft is engaged with the transmission, the hat is positioned with its protrusion facing outwardly from the integrated drive unit, with the plunger pin positioned in the hollow interior of the hat-shaped disconnect cover. The disconnect device is typically secured to the drive unit via a screw or other conventional fastener. To disengage the input shaft from the transmission, the fastener is removed so that the hat may be reversed (i.e., rotated 180xc2x0) such that the protrusion extends toward the integrated drive unit and axially displaces the plunger pin and, consequently, the input shaft, thereby disengaging the input shaft from the transmission. After repositioning the hat, the fastener is replaced so that the drive unit is maintained in its freewheel configuration. This disconnect mechanism requires the use of tools for placing the drive unit in its freewheel configuration. Utilizing a hat mechanism of this type requires the location of the appropriate tool to remove the fastener holding the hat in place and is relatively tedious to perform.
Prior art disconnect mechanisms typically extend past the hub of the drive unit and are, therefore, particularly susceptible to damage and inadvertent contact by external influences, such as rocks, mud and vegetation, for example. These influences can bind the disconnect mechanism and create an impediment to proper disconnect operation. Mechanisms of this type utilize axially exerted force (with respect to the input shaft) to effect disconnection and can be difficult to operate.
What is needed in the art is a disconnect mechanism for use with a drive unit which disconnect mechanism is quick and easy to utilize without requiring the use of tools.
What is further needed in the art is a disconnect mechanism for use with a drive unit which provides an operator with tactile indication of engagement and disengagement of the transmission.
What is additionally needed in the art is a disconnect mechanism for use with a drive unit that is protected from external influences such as, e.g., rocks, mud, and vegetation.
The foregoing shortcomings of the prior art are addressed and overcome by the present invention. The present invention provides a rotating disconnect knob having an annular helical surface (i.e., ramp surface) for placing the input shaft of a drive unit in either an engaged or a disengaged position with respect to the transmission. The disconnect knob of the current invention is manually actuatable and provides a quick and easy mechanism for placing a drive unit in a freewheel configuration.
The rotating disconnect knob of the present invention is applicable to an integrated drive unit including a fixed spindle and a rotatable hub connected to a wheel. The integrated drive unit includes a drive mechanism (e.g., hydraulic motor) for selectively driving the hub, and an output/input shaft combination for transmitting power output from the drive mechanism to power input to the transmission. The output/input shaft combination comprises an output shaft rotatably fixed to an input shaft such that relative axial movement may be effected. The input shaft is selectively axially displaceable from a first position in which the input shaft is drivingly connected to the hub (via the transmission) to a second position in which the input shaft is disconnected from the transmission, and, thus, the hub. The annular helical, or ramped surface of the disconnect knob is operable to axially displace the input shaft between the first and the second positions. In one exemplary embodiment, the rotating disconnect knob of the present invention contacts the input shaft via a plunger pin. In this embodiment, the disconnect knob includes an engage detent and a disengage detent for signaling achievement of the first and second positions of the disconnect knob, respectively. The disengage knob is positioned within a counterbore formed in the hub, and is thereby generally protected from external influences such as, e.g., rocks, mud, and vegetation.
The rotating disconnect knob of the present invention is equally applicable to a wheel drive unit including a fixed spindle and a rotatable hub connected to a wheel. The wheel drive unit generally includes a sleeve for selectively connecting an input shaft to a power source mounted outside the wheel drive unit housing. The input shaft is axially displaceable relative to the sleeve from a first position in which the input shaft is drivingly connected to the hub (via the transmission) to a second position in which the input shaft is disconnected from the transmission, and, thus, the hub. As in the case of an integrated drive unit, the annular helical, or ramped surface of the disconnect knob is operable to axially displace the input shaft between the first and the second positions.
The invention, in one form thereof, comprises a drive unit including a fixed spindle connectable to a vehicle and a rotatable hub connected to a wheel. In this form of the current invention, the drive unit comprises a gear set operable to be selectively driven by a power source, with the hub selectively operably coupled to the power source through the gear set; an input shaft for selectively connecting the power source to the gear set, with the input shaft being selectively axially displaceable from an engaged position in which the input shaft is drivingly engaged with the gear set to a disengaged position in which the input shaft is disengaged from the gear set. An actuatable ramped surface is connected to the input shaft so that actuation of the ramped surface operates to axially displace the input shaft between the engaged and disengaged positions.
The invention, in another form thereof, comprises a method of placing a drive unit in a freewheel position, wherein the drive unit includes a fixed spindle and a rotatable hub connected to a wheel; the drive unit further includes a gear set selectively driven by a power source, with the hub selectively operably coupled to the power source through the gear set; an input shaft for selectively connecting the power source to the gear set; wherein the input shaft is selectively axially displaceable from an engaged position in which the input shaft is drivingly engaged with the gear set to a disengaged position in which the input shaft is disengaged from the gear set; and an actuatable ramped surface connected to the input shaft, whereby actuation of the ramped surface operates to axially displace the input shaft between the engaged and the disengaged positions; said method comprising the step of: actuating the ramped surface.
An advantage of the present invention is the ability to place a drive unit in a freewheel configuration without the use of tools.
Another advantage of the present invention is the provision of a manually operable mechanism for placing a drive unit in a freewheel condition, which manually operable mechanism includes tactile feedback indicative of the freewheel condition.